1. Field of the Invention
This invention relates to a method and apparatus for determining the "remaining energy capacity versus voltage" curve of a battery while installed in an apparatus. More specifically, this invention relates a method and apparatus for determining a battery type, chemical composition, voltage level, current use, and remaining battery power of a battery while it is installed and in use in an electronic apparatus.
2. Description of the Related Art
Ever since batteries were invented, determining exactly how much longer a battery will last before a replacement battery is necessary has been difficult. Many devices and techniques have been used to determine the energy remaining in a battery. For example, there have been devices that measure the voltage across a battery while it is in service thereby providing a user with a voltage read-out. This type of system is ok, but batteries tend to hold a voltage while they are in use and then exponentially drop their output voltage just prior to the battery's total energy discharge. Thus, the user has very little warning before a battery goes dead.
Other systems mechanically code batteries so that the battery type is read when the battery is installed into an apparatus. Once the battery type is known then a remaining charge v. voltage curve can be determined for the specific battery type. The coding consists of metal bands about the battery which complete circuits when the battery is installed into a device. Depending on what circuits are completed when the battery is installed, the apparatus can determine whether the battery is a nicadmium, lithium, acid, alkaline, and/or determine the battery voltage output curve based on the battery type. Other techniques for coding a battery have included installing digital circuits into the battery pack to provide a digital output when the battery is installed, installing magnetic strips into a battery pack, installing light reflective surfaces which encode a battery type.